The committee voted along party lines, 12-10, to approve the nominee, Rhea Suh, to be assistant secretary for Fish and Wildlife and Parks at the Interior Department. Ms. Suh now advances to the full Senate where she needs 51 votes for confirmation. It was the first nomination meeting presided over by Ms. Landrieu.

“I am sorry we are starting this new era of the Committee on such a troubling note,” Senate Energy and Natural Resources Ranking Member Lisa Murkowski (R., Alaska) told her usual ally Ms. Landrieu. “I expect that we will be able to work together on many issues that come before us—but this particular nomination is simply not one of them.”

Ms. Murkowski and other Republicans say that Ms. Suh, who is currently Interior Assistant Secretary for Policy, Management and Budget, would push an agenda that opposes oil and natural gas development. They particularly point to comments she made in 2007 that were critical of gas.

“The pace and magnitude of this [natural gas] development is easily the single greatest threat to the ecological integrity of the West,” Ms. Suh said while working on conservation issues at the William and Flora Hewlett Foundation.

Despite facing criticism from Republicans on the campaign trail and inside Congress, Ms. Landrieu, who is in a tight re-election this year, defended Ms. Suh. Her office sent out a release rebutting the arguments put forth by Republicans as to why Ms. Suh should not be confirmed. Sen. Mark Udall, (D., Colo.), who is also up for re-election this year, also supported her nomination despite a letter the Republican delegation from Colorado—including his top challenger Rep. Cory Gardner, (R., Colo.)—sent to the energy committee on Wednesday criticizing Ms. Suh.

Opening the hearing, Thursday Ms. Landrieu again defended Ms. Suh and referenced comments she made at her initial hearing before the committee several weeks ago.

“This position is charged not with overseeing energy production, but overseeing fish, wildlife and parks,” Ms. Landrieu said Thursday. “Ms Suh. repeatedly reiterated her support for natural-gas production in front of this committee.”

Ms. Landrieu’s support is critical in getting Ms. Suh across the finish line in the full Senate. Other energy-state Democrats up for re-election, including Mark Pryor of Arkansas, Mark Begich of Alaska and Kay Hagan of North Carolina, are more likely to support Ms. Suh in the full Senate now that Ms. Landrieu has. To get 51 votes for passage without any GOP, all Democrats must vote yes. In another sign Ms. Suh will get confirmed, Sen. Joe Manchin (D., W.Va.), who is perhaps the most conservative Democrat on energy issues, also supported Ms. Suh in the committee vote on Thursday.

Given that even the most conservative Democrats seem likely to support Ms. Sun on the floor, Republicans don’t have a lot of options to further block her nomination. A senator can still put a hold on her nomination, but it’s unclear whether the loudest critics of Ms. Suh intend to do that.

“Sen. Murkowski is considering all her options, but recognizes that since the rules changes by the majority leader, that those options are limited,” said Robert Dillon, a spokesman for Ms. Murkowski.

Ms. Murkowski is particularly concerned about Ms. Suh’s decision-making authority over whether to build a road through a wildlife refuge to King Cove, a relatively isolated 1,000-person community on the Alaskan peninsula. If confirmed, Ms. Suh would head the Interior Department division that has been opposing the road to King Cove because of the potential impact on the Izembek National Wildlife Refuge.

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